Over time, dlmfs has added some features that were not part of theinitial ABI. Unfortunately, some of these features are not detectablevia standard usage. For example, Linux's default poll always returnsPOLLIN, so there is no way for a caller of poll(2) to know when dlmfsadded poll support. Instead, we provide this list of new capabilities.

Capabilities is a read-only attribute. We do it as a module parameterso we can discover it whether dlmfs is built in, loaded, or even notloaded (via modinfo).

The ABI features are local to this machine's dlmfs mount. This isdistinct from the locking protocol, which is concerned with inter-nodeinteraction.

++/*+ * These are the ABI capabilities of dlmfs.+ *+ * Over time, dlmfs has added some features that were not part of the+ * initial ABI. Unfortunately, some of these features are not detectable+ * via standard usage. For example, Linux's default poll always returns+ * POLLIN, so there is no way for a caller of poll(2) to know when dlmfs+ * added poll support. Instead, we provide this list of new capabilities.+ *+ * Capabilities is a read-only attribute. We do it as a module parameter+ * so we can discover it whether dlmfs is built in, loaded, or even not+ * loaded.+ *+ * The ABI features are local to this machine's dlmfs mount. This is+ * distinct from the locking protocol, which is concerned with inter-node+ * interaction.+ */+#define DLMFS_CAPABILITIES ""+extern int param_set_dlmfs_capabilities(const char *val,+ struct kernel_param *kp)+{+ printk(KERN_ERR "%s: readonly parameter\n", kp->name);+ return -EINVAL;+}+static int param_get_dlmfs_capabilities(char *buffer,+ struct kernel_param *kp)+{+ return strlcpy(buffer, DLMFS_CAPABILITIES,+ strlen(DLMFS_CAPABILITIES) + 1);+}+module_param_call(capabilities, param_set_dlmfs_capabilities,+ param_get_dlmfs_capabilities, NULL, 0444);+MODULE_PARM_DESC(capabilities, DLMFS_CAPABILITIES);++ /* * decodes a set of open flags into a valid lock level and a set of flags. * returns < 0 if we have invalid flags-- 1.6.6.1